Read/Write (R/W). R/W=0: Write, R/W=1: Read (This pin is
optional due to the fact that most of the time you will only want to
write to it and not read. Therefore, in general use, this pin will be
permanently connected directly to ground.)

Clock (Enable). Falling edge triggered

Bit 0 (Not used in 4-bit operation)

Bit 1 (Not used in 4-bit operation)

Bit 2 (Not used in 4-bit operation)

Bit 3 (Not used in 4-bit operation)

Bit 4

Bit 5

Bit 6

Bit 7

Backlight Anode (+) (If applicable)

Backlight Cathode (-) (If applicable)

Nominal operating voltage for LED backlights is 5V at full
brightness, with dimming at lower voltages

The HD44780 interface allows for two modes of operation, 8-bit
and 4-bit.
The operation mode must always be set using the Function Set command,
it is not defined at power-up whether the chip is in 8-bit or 4-bit
mode. For this reason, in 4-bit mode a command is sent in two
operations. To enable 4-bit mode the Function Set command must be sent
three times. Once in 4-bit mode, character and control data are
transferred as pairs of 4-bit "nibbles" on the upper data pins, D4-D7.